ScopeBridge v1.2.0

• Settings in ~/.scopebridgerc: [server] (the scope's source, port,
  listen address, web port) and [client] (where the server is), for every
  program; command-line options win over it. With [client] host set to a
  Raspberry Pi, a plain scopebridge opens the scope there. An example:
  contrib/scopebridgerc.example.
• scopebridge-server without a source looks for the scope on USB, and the
  service follows ~/.scopebridgerc.
• The web page has an About box too, with the version and the same
  animated scope screen as the GTK GUI's.
• Two more Arduino examples, with bench cases: pwm.c, PWM in hardware and
  in software side by side (jitter, outliers, harmonics), and
  irq_latency.c, the time from a hardware event to the interrupt's first
  line, with the outliers of a critical section.
• Fixed: both GUIs showed the values of a measurement still on its way
  after the measurements had been switched to another channel, or off.
• Fixed, in Python: Scope.single() returns once the scope has left the
  stopped state of an earlier acquisition, so that wait_for_trigger() can
  no longer mistake that for the new one and read an empty memory; an
  empty capture is now a clear error.
• The environment variables are SCOPEBRIDGE_HOST, SCOPEBRIDGE_PORT and
  SCOPEBRIDGE_WEB (before: RIGOL_HOST, RIGOL_PORT, RIGOL_WEB).